How Local Lands and Soils Affect Landscape Design

Updated on October 20, 2014

The elements of nature combine
together to create the environment within which a homeowner will be
designing (or redesigning) their landscape. These elements include
the form or shape of the surrounding land, the type/s of soil that
make up the landscape site, the amount and nature of water available,
the amount of sunlight or shade available, and the types of little
critters that live there (to be dealt with in another article).

Rain, sun, wind, and temperature are elements that combine to form the local "climate." They are all present in the individual landscape as well. Depending on what already exists on a property, there may be several mini- or micro-climates also that, taken into account in design, could provide some real interest in the landscape when planted according to what they offer. We will address each of these elements separately below.

Land Forms

In Southern California, where I
live, the existing land forms are mountains, grasslands, oceanside,
and the desert. Houses in Southern California are planted in all of
those locations, usually to their benefit, sometimes to their
detriment. In Southern California there is also the occasional
earthquake, which has a way of shaking up those who live nearby.
Earthquakes can topple houses and also unstable or unhealthy trees. Landscapes near earthquake faults, which are many, should consider
its possibility when choosing which types of trees to plant and where
to place them. Structures in those areas are designed and built with
resistance to earthquakes in mind and there is no reason why
landscapes should not be planned in the same way.

Hiking in the San Gabriel Mountains.

Mountains have a tendency to let
things slide, especially after a good rain. And if that rain happens
to follow a massive forest fire, also common in Southern California,
homes located in the foothills could be washed away or at least given
a good bath. This provides some free quantities of healthy topsoil,
even as it threatens the existing garden. Designing the landscape
with floods in mind and the possibility of mudslides would also be a
good idea in such areas.

Driving by a grassland north of Ojai.

Grassland areas, on the other
hand, are easy to plan for. They are generally flat, rather than
sloped, have a substantial aquafir beneath (or used to), bringing the
potential for water availability, have plenty of sunlight, and have
pretty much already been built over. This generally means that you
will be dealing with a redesign, rather than designing from scratch.
Redesigns mean that you will either have to remove the original
landscape components or include them in the new design.

Oceanside inhabitants.

Oceanside locations have also already been taken, being a favored site for good views. These sites are also extremely vulnerable to erosion, usually from ocean spray or wind, but also in the future from the rising ocean. As land-bound glaciers melt and water flows into the ocean, which is happening with increasing speed, it causes a rise in sea level. Tsunamis have not affected the area yet, but with the rising of the seas, who knows?

Looking out over the Mojave Desert.

The remaining land form, the
desert, is what all of Southern California is turning itself into by using up the groundwater and blocking its replacement. The desert, east of the San Gabriel Mountains,
is typified by rocky soil and little surface water, and by wide open,
very blue skies and not much rain. Temperatures are more extreme than
the rest of Southern California and the air is drier. All of these factors require a very
different type of planting.

Soil Types

Most plants grow in soil, which is where their nutrition comes from. Soil comes in various types and levels of compactness. The more compact the soil, the harder it is for water to sink in and roots to grow down into. Soil is made of rock ground fine and mixed with old plant material. Rocks contain nutrients that plants can feed on, but only if it's broken down by rock-eating micro-organisms first, or worn down by water or wind erosion.

Some plants prefer the coarser soils like sand, while others prefer the finer soils like loam (lots of vegetable matter) or clay (really fine and compact). Identifying the types of soil present in whatever site you want to plant is one of the first and most overlooked steps a landscape designer needs to take. There are many reasonably priced soil identification kits sold in hardware stores and the purchase and subsequent use of one can save you a lot of trouble and money later on, as you choose plants compatible with the different soil types in your yard. If the soil is too hard for any plant, compost can be added to soften it as a last resort.

Terrain of Southern California

Soil Test Kits

Groundwater

In the Antelope Valley, where I
used to live, there was once a fairly high groundwater level hidden
by sand, rocks, and native grasses. When early settlers displaced the
Mojave Indians and started mining the area, they discovered the
aquafir and brought in farmers. Alfalfa farmers liked the
area especially, but within 100 years had proliferated so much that
they had sucked the aquafir dry with their
water-hungry crop. When I moved there as a teenager in
1964 there were around 15 alfalfa farmers left. When I moved back in
1995 there were only two.

Flowing down from the mountains.

Sinking down into the aquafir.

Too much irrigation uses it all up.

Water comes in the form of rain,
which flows down the hills and across the land to fill crevices and
valleys and flow out to the sea. When crevices wind in giant curves,
the flow of water filling them, turning them into streams, slows
down. As the water slows it deposits silt from the mountains, which
replenishes the local soil, and it begins to sink down into the
ground itself, the soil there absorbing it like a sponge. This spongy
soil, with its deeply underlying layer of rock, becomes a giant water
storage basin.

When the Spaniards first settled
the area in the early 1800's, they discovered fountains and springs
and streams. They planted groves of fruit trees and dates and other
crops. Then American settlers came from the east, first by trickles,
then by droves, and the construction and populations that replaced
the farms and orchards sucked up the groundwater until there was
hardly any left. This is where it stands today.

Water is a precious resource
that any gardener needs to use judiciously. Choose plants that fit
with the amount of water available. Let the prevalence of rain be
your guide. Depending on irrigation to water your yard perpetuates
the problem created by those who came before you.